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Untangling physics: Knots in water, light and the sun

By Leonie Mueck

From our star’s excess heat to the complexities of fluid turbulence, many a mystery might be unravelled by the bane of the headphone wearer – knots

PERHAPS it was the foul stench that inspired William Thomson to one of his oddest ideas. In 1867, the physicist, now better known as Lord Kelvin, was observing his colleague Peter Guthrie Tait producing smoke rings from ammonia, sulphuric acid and salt in his Edinburgh laboratory. As the rings glided across the room with elegant stability, a thought struck Thomson&colon; was this what matter was made of?

What if atoms weren’t solid spheres, as most gentleman scientists then believed, but looped vortices tied in the field of the lumeniferous aether, the medium then thought to carry light waves? That might explain why atoms absorb light. And as for the different chemical elements – why, they would just be ever more complex sorts of knots.

Thinking they were constructing a table of the elements, Tait and others went on to busy themselves classifying all the different sorts of knots by their number of loops and crossings, thus founding the modern mathematical discipline of knot theory. Sadly, though, the underlying idea was soon undone&colon; apart from anything else, experiments two decades later showed the lumeniferous aether didn’t exist.

But the basis of Thomson’s ruminations has been bugging some physicists ever since. Can you actually tie a knot in anything so ethereal as a field – be it light, gravity or anything else? It has taken a century and a half, but now it seems we have an answer.